I got it on the first wave of 3, I sat in my starting point and let them get into cover, then i destroyed the cover used by the enemy on my left, he ran over to his left by where the other 2 guys were at and got in that little "glitch" where he just ran back and forth in the small platform...that might work every time, or take a few tries I'm not sure.

Took me about three times at the start of the library just before you start the final boss. Just remember to take out most of the other colors while using cover in the elevator. Once you have about 4 or 5 of the TESTERS just unload your grenade launcher. Chances are you will hit three of them. I actually died when the achievement popped. Also, if you do not get it make sure that you leave a guy alive in that room. Otherwise the final boss fight scene automatically starts.

After following the several posted suggestions for this achievement for about 3 hours, I decided to try JordBrett's advice and it worked for me.

Observe the Grenade 15
Kill three Testers with one grenade launcher shot. "Test the grenades: check!"

---"Use the room right before the boss battle (you take an elevator up and when you exit, there's a bookcase directly in front of you). ---On your left is a red guy and to the right is a pink. Step forward and kill the red guy, then back up back into the elevator to prevent the pink guy from going behind you. ---Look right and kill the yellow guy. Hopefully, all the pink testers will be on the right. Grab the Max Hazard pickup on the left side of the room. ---Take cover on the left side of the initial bookcase, aim around and hit the pink tester in the middle."

This will be the most aggravating and frustrating achievement in the game. If you got it without trying, then you got lucky. Go luck everyone.

Oh my god, that was a f***er to get, just keep trying and fire off 2-3 genades just to be sure. I think the game just gave me the achievement coz it was boring of reloading the same it over and over.

Don't know about everyone else, but I actually enjoyed playing this, some quite funny moments to be had (love the space marine that forgot to pick stuff up and had inverted controls)

Man, I am not gonna lie, this achievement is a total pain in the ass! I finally got it though using the tips in this thread. Finally finished this damn game. Thanks for the tip about the room before the boss fight, that is where I got it.

I just found a very nice way to do this. At at the start of the testers area (in final boss battle) there will be 3 to start with. Take cover that is immediately in front of you (down the stairs) and the testers will take cover just past that (basically in a line). Kill the one closest to you. In a couple of seconds, a new tester will spawn and run towards you to replace the one you just killed. Wait until he is right between the other two and fire. I got this on my very first run-through of the game in about 2 tries.

this chevo took me about 20 attempts , dont give up and keep shooting grenades cos there are quite a few pinks and you dont have to get them all in 1 shot, i took 8 grenades with me and i'm glad i did!!

For me I did it in the library. Made sure I got the hazard upgrade and activated the power up then shot like hell at the pinkys. They didn't die at the same time but died one after another pretty quick. Thanks to this thread I was able to get it.

Took me about 25 minutes, Final Boss Battle is definitely the best place, since if you kill 1 or 2 testers more will spawn. As others have said, best thing to do is to take out their cover and force them towards one side. If you take out MOST of the cover on one of the switch platforms, and take up position there, and slowly take out everything they stand behind, eventually they'll just stand in place and wander slowly towards you, when this happens, position yourself with the blue force field that is blocking the third switch between yourself and them, and wait, they'll clump together on the stairs after a while and make the achievement easy, just hit any of the 3 and the other 2 will fly off the sides.

After following the several posted suggestions for this achievement for about 3 hours, I decided to try JordBrett's advice and it worked for me.

Observe the Grenade 15
Kill three Testers with one grenade launcher shot. "Test the grenades: check!"

---"Use the room right before the boss battle (you take an elevator up and when you exit, there's a bookcase directly in front of you).
---On your left is a red guy and to the right is a pink. Step forward and kill the red guy, then back up back into the elevator to prevent the pink guy from going behind you.
---Look right and kill the yellow guy. Hopefully, all the pink testers will be on the right. Grab the Max Hazard pickup on the left side of the room.
---Take cover on the left side of the initial bookcase, aim around and hit the pink tester in the middle."
This will be the most aggravating and frustrating achievement in the game. If you got it without trying, then you got lucky. Go luck everyone.

OMG i did it follow this and you will eventually get them together... it will happen it took me about 2 hours but i go it now :w oop:

Easy Achievement, if you ask me
Tried it 3 times and my mehtod worked every time.

Did it in the room befor the boss battle, too.

Run out of the elevator
kill the left guy
let the right one run to the left side and behind the wall in the middle of the room.
wait there till the guy on the right side, near the pillar, appears.
(There should be 2 guys behind the wall right now)
Run past the pillar guy
turn around
one of the 2 guys on the left now run into the middle
aim for him and kill him before he runs behind the wall

easy

__________________

Third in Germany to 1000 Batman: AA
First in Germany to 1000 Batman: AC

Many thanks to the several good suggestions here. Managed to get it in around 10 minutes with these tips after 2 hours of trying to get those pink suckers to cluster up! On to Maximum Hazzard and the last two achievements.

Observe the Grenade 15
Kill three Testers with one grenade launcher shot. "Test the grenades: check!"

---"Use the room right before the boss battle (you take an elevator up and when you exit, there's a bookcase directly in front of you).
---On your left is a red guy and to the right is a pink. Step forward and kill the red guy, then back up back into the elevator to prevent the pink guy from going behind you.
---Look right and kill the yellow guy. Hopefully, all the pink testers will be on the right. Grab the Max Hazard pickup on the left side of the room.
---Take cover on the left side of the initial bookcase, aim around and hit the pink tester in the middle."

Alright, I share the pain and frustration you get from this achievement so I will summarize what I did and see if it helps anyone else...

Minimum Hazard - Last Level - Boss Fight - 3rd Wave (with all of the testers)
So quickly switch to 'nade launcher, run up to small end of sand bag pile and just stand there (do not take cover), wait, pay attention to their movements. One will run right up to you but resist the urge to pull the trigger until he has almost reached cover behind the missle thing to your right. NOW blow him up then continue to launch as you move your crosshairs to the man running up the stairs as he does the other one will be near the box to your left and almost behind cover, once the guy on the stairs is hit swing your cross hairs over to the upper right corner of that box, if the man hiding there is not dead already he will be.
7 Grenades, 3 Testers, 2 Tries and 15G. Done.

I believe this is the easiest way. 3 tries and 4 grenades (I missed one shot), 3 minutes. Here is what I did.

On the boss battle with weasel or whatever his name is :P, after you run up and hit the second switch on the right of the area you are fighting his hench men in, as SOON as you are exiting the switch area after you have hit it there should be (I believe) a missile launcher cover thing, that is if you didnt take cover behind it on the way to the switch and it got de-resed, so try to avoid this. Take cover behind it (granted it didnt get de-resed). Now there should immediately spawn 3 testers right near you, dont shoot them right away. One will run and take cover on sand bags, another will take cover behind a taller cover object right next to him, the third tester will run up the stairs and pause for a moment, basically almost right between the other two, however this tester WILL also take cover so just be leaning around your cover and ready to take the shot. This will all be happening basically right in front of you. Shoot the one that runs up the stairs WHILE they are standing still. KA-BOOM. 3 kills, 1 achievement.

In the end I just rapid-fired my grenades at the group of testers and the achievement popped without me really aiming at anything. Using one grenade would perhaps kill two testers but only damage the third. Firing a cluster would mean the first explosion damages all the testers and the second grenade is enough to kill all three.

Certainly it's down to luck. However that's another 1000g done and dusted, and another game traded in.

After following the several posted suggestions for this achievement for about 3 hours, I decided to try JordBrett's advice and it worked for me.

Observe the Grenade 15
Kill three Testers with one grenade launcher shot. "Test the grenades: check!"

---"Use the room right before the boss battle (you take an elevator up and when you exit, there's a bookcase directly in front of you).
---On your left is a red guy and to the right is a pink. Step forward and kill the red guy, then back up back into the elevator to prevent the pink guy from going behind you.
---Look right and kill the yellow guy. Hopefully, all the pink testers will be on the right. Grab the Max Hazard pickup on the left side of the room.
---Take cover on the left side of the initial bookcase, aim around and hit the pink tester in the middle."

Be sure to shoot the grenade launcher more than once. Sometimes you'll still be able to unlock the achievement even if you've shot more than once. Keep trying. You'll get it.
This will be the most aggravating and frustrating achievement in the game. If you got it without trying, then you got lucky. Go luck everyone.

I just did exactly what you said word for word, and close to two years since I played I maxed this game out, thanks

__________________Captain America - Tell me you didn't just kill them!Zemo - A worse fate even then that. I sent them to Bayonne, New Jersey.
- Marvel Civil War Comic

"I did it! I actually KILLED 3 testers with a single grenade!" ~ spoken like Wally Wellesley when he has killed Matt Hazard.

I did this during phase 3 of the final boss fight. Right from the checkpoint, I walked down the steps and took cover behind the rocket launcher. As soon as the tester that spawns on the left walks over to the right towards another tester, I walked to the sand bags on front of me and took cover.

The third tester (who spawns the farthest away) comes walking up the steps and tries going to the left. If you are aiming just right, as the third tester reaches to top step, you can fire a grenade at him killing all three testers.

It took me three attempts at this, and the first was just witnessing their pattern. If you're having a hard time doing this any other way, I'd say try this method as it's fast and easy to reset if you fail.

I got so mad after about 45 minutes of trying to get this. I just started lobbing all 6 of my grenades out of my gun. About after 5 minutes of doing this the achievement pops. So it's time based and not grenade based. 3 kills in about a second and a half seem to be where it's at.